Methods are known in the art for glass manufacturing wherein glass-forming, batch ingredients are converted into agglomerates and these agglomerates then heated in a chamber by a direct contact with flue gases from a glass melting furnace so as to produce free-flowing, non-aggregated, agglomerates which are then conveyed and discharged to the glass melting furnace. These agglomerates are composite, integral, self-supporting masses consisting essentially of all the substantial batch materials and may take the form of balls, extrusions, discs, briquettes, and pellets. One such method is a process for making glass wherein free water-containing pellets are discharged to a vertical bed contained within a chamber and furnace flue gases pass, in direct contact with and countercurrently to, downwardly moving pellets of the bed to dry and preheat them. The flue gases enter the pellet bed on the order of about 1500.degree. F. (816.degree. C.) and the process is operated so as to prevent water in the gases from condensing in the chamber. In this manner, volatile pollutants in the flue gases are extracted and recycled to the melter via the pellets.
In contrast to the direct extraction of heat from the flue gases as they pass through the furnace, another method provides an improvement by indirectly extracting heat from the flue gases in the chamber during the heating of the agglomerated glass batch.
Because a heat transfer medium is heated by the indirect heat exchange process, the medium is ideally suited for beneficial recovery and utilization of its energy.